By optimizing combustion, the mill has been able to maximize and increase the main steam output of the biomass boiler beyond the maximum continuous rating (MCR). Other benefits include more stable and controlled boiler steam output as well as improved operational uniformity across shifts, furnace symmetry and spray valve control. Valmet's APC application estimates the British thermal units (BTU) of the biomass fuel in real time and ensures a consistent optimum fuel power-to-air ratio.

The application has lowered the average O2 by about 0.3 percentage points, which improves boiler efficiency, reduces NOXemissions and subsequently minimizes NH3 consumption. Additionally, Valmet's advanced load controller now properly allocates the fuel demand between the feeders, taking into account any control and/or mechanical process limitations.

"This improvement has enabled us to run a higher, more stable load, resulting in a record-setting steaming average the following month," says Barry Hensley, Powerhouse Superintendent, WestRock.

The combustion control application is part of the boiler plant's Valmet DNA automation system. In 2012, Valmet was chosen as the automation supplier for the new biomass bubbling fluidized bed boiler at the Covington mill. The scope of the system included the boiler, Balance of the Plant, auxiliaries and a training simulator. Valmet's strong project execution team and close cooperation with Covington personnel made it possible to meet the challenging project deadlines.

"Valmet's commitment to a shared journey forward together with the Covington mill is how the APC project came about. The ROI for the project was less than six months. With our solution and biomass expertise, and working together with the mill's personnel, we were able to exceed all the project targets," says David Eapen, Solution Manager, Automation, Valmet.

Technical information about Valmet's Advanced Process Control

Valmet DNA FBB Combustion Manager is an advanced control application for the optimized combustion of both bubbling and circulating fluidized bed boilers. The purpose of the application is to protect the combustion process against variations in production, fuel amount, fuel quality and combustion circumstances.

WestRock partners with its customers to provide differentiated paper and packaging solutions that help them win in the marketplace. WestRock's 39,000 team members support customers around the world from more than 250 operating and business locations spanning North America, South America, Europe and Asia.

Valmet is the leading global developer and supplier of process technologies, automation and services for the pulp, paper and energy industries. We aim to become the global champion in serving our customers.

Valmet's strong technology offering includes pulp mills, tissue, board and paper production lines, as well as power plants for bioenergy production. Our advanced services and automation solutions improve the reliability and performance of our customers' processes and enhance the effective utilization of raw materials and energy.

Valmet's net sales in 2016 were approximately EUR 2.9 billion. Our 12,000 professionals around the world work close to our customers and are committed to moving our customers' performance forward - every day. Valmet's head office is in Espoo, Finland and its shares are listed on the Nasdaq Helsinki.

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